Cross-sectional study of 168 patients with hepatorenal tyrosinaemia and implications for clinical practice

BackgroundHepatorenal tyrosinaemia (Tyr 1) is a rare inborn error of tyrosine metabolism. Without treatment, patients are at high risk of developing acute liver failure, renal dysfunction and in the long run hepatocellular carcinoma. The aim of our study was to collect cross-sectional data.MethodsVia questionnaires we collected retrospective data of 168 patients with Tyr 1 from 21 centres (Europe, Turkey and Israel) about diagnosis, treatment, monitoring and outcome. In a subsequent consensus workshop, we discussed data and clinical implications.ResultsEarly treatment by NTBC accompanied by diet is essential to prevent serious complications such as liver failure, hepatocellular carcinoma and renal disease. As patients may remain initially asymptomatic or develop uncharacteristic clinical symptoms in the first months of life newborn mass screening using succinylacetone (SA) as a screening parameter in dried blood is mandatory for early diagnosis. NTBC-treatment has to be combined with natural protein restriction supplemented with essential amino acids. NTBC dosage should be reduced to the minimal dose allowing metabolic control, once daily dosing may be an option in older children and adults in order to increase compliance. Metabolic control is judged by SA (below detection limit) in dried blood or urine, plasma tyrosine (<400 ¿M) and NTBC-levels in the therapeutic range (20¿40 ¿M). Side effects of NTBC are mild and often transient.Indications for liver transplantation are hepatocellular carcinoma or failure to respond to NTBC. Follow-up procedures should include liver and kidney function tests, tumor markers and imaging, ophthalmological examination, blood count, psychomotor and intelligence testing as well as therapeutic monitoring (SA, tyrosine, NTBC in blood).ConclusionBased on the data from 21 centres treating 168 patients we were able to characterize current practice and clinical experience in Tyr 1. This information could form the basis for clinical practice recommendations, however further prospective data are required to underpin some of the recommendations.

Unstable argininosuccinate lyase in variant forms of the urea cycle disorder argininosuccinic aciduria.

Loss of function of the urea cycle enzyme argininosuccinate lyase (ASL) is caused by mutations in the ASL gene leading to ASL deficiency (ASLD). ASLD has a broad clinical spectrum ranging from life-threatening severe neonatal to asymptomatic forms. Different levels of residual ASL activity probably contribute to the phenotypic variability but reliable expression systems allowing clinically useful conclusions are not yet available. In order to define the molecular characteristics underlying the phenotypic variability, we investigated all ASL mutations that were hitherto identified in patients with late onset or mild clinical and biochemical courses by ASL expression in human embryonic kidney 293 T cells. We found residual activities >3 % of ASL wild type (WT) in nine of 11 ASL mutations. Six ASL mutations (p.Arg95Cys, p.Ile100Thr, p.Val178Met, p.Glu189Gly, p.Val335Leu, and p.Arg379Cys) with residual activities ≥16 % of ASL WT showed no significant or less than twofold reduced Km values, but displayed thermal instability. Computational structural analysis supported the biochemical findings by revealing multiple effects including protein instability, disruption of ionic interactions and hydrogen bonds between residues in the monomeric form of the protein, and disruption of contacts between adjacent monomeric units in the ASL tetramer. These findings suggest that the clinical and biochemical course in variant forms of ASLD is associated with relevant residual levels of ASL activity as well as instability of mutant ASL proteins. Since about 30 % of known ASLD genotypes are affected by mutations studied here, ASLD should be considered as a candidate for chaperone treatment to improve mutant protein stability.

Membranöse Glomerulopathie-eine Autoimmunerkrankung

Membranous nephropathy is one of the most common glomerular diseases and leading causes of nephrotic syndrome in Caucasian adults. Known as a clinico-pathologic entity for over 50 years, it is defined by thickening of the glomerular capillary membrane with subepithelial immuncomplexes. Secondary forms (e. g. hepatitis B, autoimmune disease or medication-induced) are distinguished from idiopathic forms. Despite spontaneous remissions in about 30 % of cases, one third of idiopathic forms progress to end-stage renal disease after 10 years. Seminal research progress of the last decade has allowed the identification of autoantibodies directed against podocytary elements leading to secondary damage to the filtration barrier. The so-called idiopathic membranous nephropathy has thus become a prototype of autoimmune disease. The autoantibodies detectable in 70 - 80 % of cases of idiopathic membranous nephropathy are directed against the M-type phospholipase A2-receptor on the podocyte membrane and correlate with disease activity. These epochal findings influence on diagnostic and therapeutic strategies establishing a rationale for the use of B cell-directed therapy on top of optimal supportive therapy.

Patient safety in dialysis access

Not only are dialysis access creation and maintenance prone to complications, but patients suffering from end-stage renal disease and its comorbidities generally have a high risk of adverse events during their continuous treatment. Preventive strategies are key to avoid harm and to improve the outcome of the treatment of the growing number of patients with chronic kidney failure, especially as doctors and nurses are not always aware of the consequences of unsafe behavior. This publication is intended for health care professionals – nurses as well as doctors – and aims to raise the awareness of patient safety aspects, combining medical education with evidence-based medicine. After a general overview of the topic, an international panel of authors provides a diversified insight into important concepts and technical tricks essential to create and maintain a functional dialysis access. Contributions to Nephrology, Vol. 184

Genome-wide Association Studies Identify Genetic Loci Associated with Albuminuria in Diabetes

Elevated concentrations of albumin in the urine, albuminuria, are a hallmark of diabetic kidney disease and associate with increased risk for end-stage renal disease and cardiovascular events. To gain insight into the pathophysiological mechanisms underlying albuminuria, we conducted meta-analyses of genome-wide association studies and independent replication in up to 5,825 individuals of European ancestry with diabetes mellitus and up to 46,061 without diabetes, followed by functional studies. Known associations of variants in CUBN, encoding cubilin, with the urinary albumin-to-creatinine ratio (UACR) were confirmed in the overall sample (p=2.4*10(-10)). Gene-by-diabetes interactions were detected and confirmed for variants in HS6ST1 and near RAB38/CTSC. SNPs at these loci demonstrated a genetic effect on UACR in individuals with but not without diabetes. The change in average UACR per minor allele was 21% for HS6ST1 and 13% for RAB38/CTSC (p=6.3*10(-7) and 5.8*10(-7), respectively). Experiments using streptozotocin-treated diabetic Rab38 knockout and control rats showed higher urinary albumin concentrations and reduced amounts of megalin and cubilin at the proximal tubule cell surface in Rab38 knockout vs. control rats. Relative expression of RAB38 was higher in tubuli of patients with diabetic kidney disease compared to controls. The loci identified here confirm known and highlight novel pathways influencing albuminuria.

Is there an age cutoff to apply adult formulas for GFR estimation in children?

BACKGROUND Estimation of glomerular filtration rate (eGFR) using a common formula for both adult and pediatric populations is challenging. Using inulin clearances (iGFRs), this study aims to investigate the existence of a precise age cutoff beyond which the Modification of Diet in Renal Disease (MDRD), the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI), or the Cockroft-Gault (CG) formulas, can be applied with acceptable precision. Performance of the new Schwartz formula according to age is also evaluated. METHOD We compared 503 iGFRs for 503 children aged between 33 months and 18 years to eGFRs. To define the most precise age cutoff value for each formula, a circular binary segmentation method analyzing the formulas' bias values according to the children's ages was performed. Bias was defined by the difference between iGFRs and eGFRs. To validate the identified cutoff, 30% accuracy was calculated. RESULTS For MDRD, CKD-EPI and CG, the best age cutoff was ≥14.3, ≥14.2 and ≤10.8 years, respectively. The lowest mean bias and highest accuracy were -17.11 and 64.7% for MDRD, 27.4 and 51% for CKD-EPI, and 8.31 and 77.2% for CG. The Schwartz formula showed the best performance below the age of 10.9 years. CONCLUSION For the MDRD and CKD-EPI formulas, the mean bias values decreased with increasing child age and these formulas were more accurate beyond an age cutoff of 14.3 and 14.2 years, respectively. For the CG and Schwartz formulas, the lowest mean bias values and the best accuracies were below an age cutoff of 10.8 and 10.9 years, respectively. Nevertheless, the accuracies of the formulas were still below the National Kidney Foundation Kidney Disease Outcomes Quality Initiative target to be validated in these age groups and, therefore, none of these formulas can be used to estimate GFR in children and adolescent populations.

Risk factors for encephalitis and death from West Nile virus infection: An analysis of hospitalized cases in Houston, Texas from 2002--2008

We conducted a nested case-control study to determine the significant risk factors for developing encephalitis from West Nile virus (WNV) infection. The purpose of this research project was to expand the previously published Houston study of 2002–2004 patients to include data on Houston patients from four additional years (2005–2008) to determine if there were any differences in risk factors shown to be associated with developing the more severe outcomes of WNV infection, encephalitis and death, by having this larger sample size. A re-analysis of the risk factors for encephalitis and death was conducted on all of the patients from 2002–2008 and was the focus of this proposed research. This analysis allowed for the determination to be made that there are differences in the outcome in the risk factors for encephalitis and death with an increased sample size. Retrospective medical chart reviews were completed for the 265 confirmed WNV hospitalized patients; 153 patients had encephalitis (WNE), 112 had either viral syndrome with fever (WNF) or meningitis (WNM); a total of 22 patients died. Univariate logistic regression analyses on demographic, comorbidities, and social risk factors was conducted in a similar manner as in the previously conducted study to determine the risk factors for developing encephalitis from WNV. A multivariate model was developed by using model building strategies for the multivariate logistic regression analysis. The hypothesis of this study was that there would be additional risk factors shown to be significant with the increase in sample size of the dataset. This analysis with a greater sample size and increased power supports the hypothesis in that there were additional risk factors shown to be statistically associated with the more severe outcomes of WNV infection (WNE or death). Based on univariate logistic regression results, these data showed that even though age of 20–44 years was statistically significant as a protecting effect for developing WNE in the original study, the expanded sample lacked significance. This study showed a significant WNE risk factor to be chronic alcohol abuse, when it was not significant in the original analysis. Other WNE risk factors identified in this analysis that showed to be significant but were not significant in the original analysis were cancer not in remission > 5 years, history of stroke, and chronic renal disease. When comparing the two analyses with death as an outcome, two risk factors that were shown to be significant in the original analysis but not in the expanded dataset analysis were diabetes mellitus and immunosuppression. Three risk factors shown to be significant in this expanded analysis but were not significant in the original study were illicit drug use, heroin or opiate use, and injection drug use. However, with the multiple logistic regression models, the same independent risk factors for developing encephalitis of age and history of hypertension including drug induced hypertension were consistent in both studies.^

Diabetic nephropathy in African-Americans with type 1 diabetes: The new Jersey 725 study

Diabetic nephropathy is the most common cause of end-stage renal disease (ESRD) in the United States. African-Americans and patients with type 1 diabetes (T1D) are at increased risk. We studied the rate and factors that influenced progression of glomerular filtration rate (GFR) in 401 African-American T1D patients who were followed for 6 years through the observational cohort New Jersey 725 study. Patients with ESRD and/or GFR<20 ml/min were excluded. The mean (SD) baseline GFR was 106.8 (27.04) ml/min and it decreased by 13.8 (mean, SD 32.2) ml/min during the 6-year period (2.3 ml/min/year). In patients with baseline macroproteinuria, GFR decreased by 31.8 (39.0) ml/min (5.3 ml/min/year) compared to 8.2 (mean, SD 27.6) ml/min (1.3 ml/min/year) in patients without it (p<0.00001). Six-year GFR fell to <20 ml/min in 5.25% of all patients, but in 16.8% of macroproteinuric patients.^ A model including baseline GFR, proteinuria category and hypertension category, explained 35% of the 6-year GFR variability (p<0.0001). After adjustment for other variables in the model, 6-year GFR was 24.9 ml/min lower in macroproteinuric patients than in those without proteinuria (p=0.0001), and 12.6 ml/min lower in patients with treated but uncontrolled hypertension compared to normotensive patients (p=0.003). In this sample of patients, with an elevated mean glycosylated hemoglobin of 12.4%, glycemic control did not independently influence GFR deterioration, nor did BMI, cholesterol, gender, age at diabetes onset or socioeconomic level.^ Taken together, our findings suggest that proteinuria and hypertension are the most important factors associated with GFR deterioration in African-American T1D patients.^

Neurotrophic factors [activity-dependent neurotrophic factor (ADNF) and basic fibroblast growth factor (bFGF)] interrupt excitotoxic neurodegenerative cascades promoted by a PS1 mutation

Although an excitotoxic mechanism of neuronal injury has been proposed to play a role in chronic neurodegenerative disorders such as Alzheimer’s disease, and neurotrophic factors have been put forward as potential therapeutic agents, direct evidence is lacking. Taking advantage of the fact that mutations in the presenilin-1 (PS1) gene are causally linked to many cases of early-onset inherited Alzheimer’s disease, we generated PS1 mutant knock-in mice and directly tested the excitotoxic and neurotrophic hypotheses of Alzheimer’s disease. Primary hippocampal neurons from PS1 mutant knock-in mice exhibited increased production of amyloid β-peptide 42/43 and increased vulnerability to excitotoxicity, which occurred in a gene dosage-dependent manner. Neurons expressing mutant PS1 exhibited enhanced calcium responses to glutamate and increased oxyradical production and mitochondrial dysfunction. Pretreatment with either basic fibroblast growth factor or activity-dependent neurotrophic factor protected neurons expressing mutant PS1 against excitotoxicity. Both basic fibroblast growth factor and activity-dependent neurotrophic factor stabilized intracellular calcium levels and abrogated the increased oxyradical production and mitochondrial dysfunction otherwise caused by the PS1 mutation. Our data indicate that neurotrophic factors can interrupt excitotoxic neurodegenerative cascades promoted by PS1 mutations.

Correlation of breath ammonia with blood urea nitrogen and creatinine during hemodialysis

We have spectroscopically determined breath ammonia levels in seven patients with end-stage renal disease while they were undergoing hemodialysis at the University of California, Los Angeles, dialysis center. We correlated these measurements against simultaneously taken blood samples that were analyzed for blood urea nitrogen (BUN) and creatinine, which are the accepted standards indicating the level of nitrogenous waste loading in a patient's bloodstream. Initial levels of breath ammonia, i.e., at the beginning of dialysis, are between 1,500 ppb and 2,000 ppb (parts per billion). These levels drop very sharply in the first 15–30 min as the dialysis proceeds. We found the reduction in breath ammonia concentration to be relatively slow from this point on to the end of dialysis treatment, at which point the levels tapered off at 150 to 200 ppb. For each breath ammonia measurement, taken at 15–30 min intervals during the dialysis, we also sampled the patient's blood for BUN and creatinine. The breath ammonia data were available in real time, whereas the BUN and creatinine data were available generally 24 h later from the laboratory. We found a good correlation between breath ammonia concentration and BUN and creatinine. For one of the patients, the correlation gave an R2 of 0.95 for breath ammonia and BUN correlation and an R2 of 0.83 for breath ammonia and creatinine correlation. These preliminary data indicate the possibility of using the real-time breath ammonia measurements for determining efficacy and endpoint of hemodialysis.

Alterations in the regulation of androgen-sensitive Cyp 4a monooxygenases cause hypertension

Hypertension is a leading cause of cardiovascular, cerebral, and renal disease morbidity and mortality. Here we show that disruption of the Cyp 4a14 gene causes hypertension, which is, like most human hypertension, more severe in males. Male Cyp 4a14 (−/−) mice show increases in plasma androgens, kidney Cyp 4a12 expression, and the formation of prohypertensive 20-hydroxyarachidonate. Castration normalizes the blood pressure of Cyp 4a14 (−/−) mice and minimizes Cyp 4a12 expression and arachidonate ω-hydroxylation. Androgen replacement restores hypertensive phenotype, Cyp 4a12 expression, and 20-hydroxy-arachidonate formation. We conclude that the androgen-mediated regulation of Cyp 4a arachidonate monooxygenases is an important component of the renal mechanisms that control systemic blood pressures. These results provide direct evidence for a role of Cyp 4a isoforms in cardiovascular physiology, establish Cyp 4a14 (−/−) mice as a monogenic model for the study of cause/effect relationships between blood pressure, sex hormones, and P450 ω-hydroxylases, and suggest the human CYP 4A homologues as candidate genes for the analysis of the genetic and molecular basis of human hypertension.

Qualidade de vida dos cuidadores informais de doentes de Huntington

Introdução: A Doença de Huntington (DH) é uma patologia neuro degenerativa hereditária de transmissão autossómica dominante que afeta o movimento e conduz a um défice progressivo das capacidades cognitivas e comportamentais. Cuidar um doente de Huntington é um processo complexo e exigente com um grande impacto na saúde, bem-estar e qualidade de vida do cuidador informal. Objetivo: Avaliar o impacto da DH na Qualidade de Vida do Cuidador Informal, e verificar em que medida as variáveis sociodemográficas, contextuais e clínicas se relacionam com essa Qualidade de Vida. Metodologia: Trata-se de um estudo quantitativo, não experimental, transversal numa lógica de análise descritivo-correlacional com 50 Cuidadores Informais de nacionalidade espanhola, membros da “Asociación de Corea de Huntington Española” - ACHE. Utilizamos a versão espanhola do questionário: Huntington’s Disease Quality of Life Battery for Carers (HDQoLC) como instrumento de colheita de dados especifico para a avaliação da QDV dos Cuidadores de Doentes de Huntington . Resultados: Os participantes são na sua maioria do sexo feminino (68%), com uma media de idades de 50,04 anos, casados (72%) com elevado grau de literacia (52%) e no ativo (72%). São essencialmente cônjuges da pessoa dependente (52%) ou filhos(as) (28%). Os resultados sugerem que os CI possuem uma QDV moderada (53%) na qual os “aspetos práticos do cuidar”, ou seja, o papel de cuidador, tem grande impacto na QDV (43%) a “satisfação com a vida e os “sentimentos sobre a vida com DH” parecem atenuar esta sobrecarga. Os dados obtidos revelam que as variáveis que influenciaram significativamente a Qualidade de Vida total são: as habilitações literárias e o número de horas de cuidados diários. No entanto podemos afirmar que a idade, tempo como CI e os motivos que levaram a assumir o papel de cuidador, tem uma relação expressiva com a dimensão “aspetos práticos do cuidar” da QDV. Conclusões: Os resultados reforçam a multidimensionalidade e variabilidade da qualidade de vida dos cuidadores informais de Doentes de Huntington e evidenciam a necessidade dos profissionais de saúde apostarem em programas de intervenção na comunidade, de forma a implementar estratégias de apoio que minimizem as dificuldades sentidas, aumentem a capacidade para a prestação de cuidados e que promovam a qualidade de vida dos que cuidam. Palavras-chave:; Doença de Huntington; Cuidadores Informais; Qualidade de Vida.

Effects of pathophysiological concentrations of albumin on NHE3 activity and cell proliferation in primary cultures of human proximal tubule cells

The progression of renal disease correlates strongly with hypertension and the degree of proteinuria, suggesting a link between excessive Na+ reabsorption and exposure of the proximal tubule to protein. The present study investigated the effects of albumin on cell growth and Na+ uptake in primary cultures of human proximal tubule cells (PTC). Albumin (1.0 mg/ml) increased cell proliferation to 134.1 +/- 11.8% (P < 0.001) of control levels with no change in levels of apoptosis. Exposure to 0.1 and 1.0 mg/ml albumin increased total Na-22(+) uptake to 119.1 &PLUSMN; 6.3% (P = 0.005) and 115.6 &PLUSMN; 5.3% (P < 0.006) of control levels, respectively, because of an increase in Na+/H+ exchanger isoform 3 (NHE3) activity. This was associated with an increase in NHE3 mRNA to 161.1 +/- 15.1% (P < 0.005) of control levels in response to 0.1 mg/ml albumin. Using confocal microscopy with a novel antibody raised against the predicted extracellular NH2 terminus of human NHE3, we observed in nonpermeabilized cells that exposure of PTC to albumin (0.1 and 1.0 mg/ml) increased NHE3 at the cell surface to 115.4 &PLUSMN; 2.7% (P < 0.0005) and 122.4 +/- 3.7% (P < 0.0001) of control levels, respectively. This effect was paralleled by significant increases in NHE3 in the subplasmalemmal region as measured in permeabilized cells. These albumin-induced increases in expression and activity of NHE3 in PTC suggest a possible mechanism for Na+ retention in response to proteinuria.

Glomerular number and size in autopsy kidneys: The relationship to birth weight

Background. In the Southeast United States, African Americans have an estimated incidence of hypertension and end-stage renal disease (ESRD) that is five times greater than Caucasians. Higher rates of low birth weight (LBW) among African Americans is suggested to predispose African Americans to the higher risk, possibly by reducing the number of glomeruli that develop in the kidney. This study investigates the relationships between age, race, gender, total glomerular number (N-glom), mean glomerular volume (V-glom), body surface area (BSA), and birth weight. Methods. Stereologic estimates of N-glom and V-glom were obtained using the physical disector/fractionator combination for autopsy kidneys from 37 African Americans and 19 Caucasians. Results. N-glom was normally distributed and ranged from 227,327 to 1,825,380, an 8.0-fold difference. A direct linear relationship was observed between N-glom and birth weight (r=0.423, P=0.0012) with a regression coefficient that predicted an increase of 257,426 glomeruli per kilogram increase in birth weight (alpha=0.050:0.908). Among adults there was a 4.9-fold range in V-glom , and in adults, V-glom was strongly and inversely correlated with N-glom (r=-0.640, P=0.000002). Adult V-glom showed no significant correlation with BSA for males (r=-0.0150, P=0.936), although it did for females (r=0.606, P=0.022). No racial differences in average N-glom or V-glom were observed. Conclusion. Birth weight is a strong determinant of N-glom and thereby of glomerular size in the postnatal kidney. The findings support the hypothesis that LBW by impairing nephron development is a risk factor for hypertension and ESRD in adulthood.

Practical considerations for the measurement of free light chains in serum

Background: A new immunoassay for free light chain measurements has been reported to be useful for the diagnosis and monitoring of monoclonal light chain diseases and nonsecretory myeloma. We describe experience with and some potential pitfalls of the assay. Methods: The assay was assessed for precision, sample type and stability, recovery, and harmonization of results between two analyzers on which the reagents are used. Free-light-chain concentrations were measured in healthy individuals (to determine biological variation), patients with monoclonal gammopathy of undetermined significance, myeloma patients after autologous stem cell transplants, and patients with renal disease. Results: Analytical imprecision (CV) was 6-11% for kappa and A free-light-chain measurement and 16% for the calculated kappa/lambda ratio. Biological variation was generally insignificant compared with analytical variation. Despite the same reagent source, values were not completely harmonized between assay systems and may produce discordant free-light-chain ratios. In some patients with clinically stable myeloma, or post transplantation, or with monoclonal gammopathy of undetermined significance, free-light-chain concentration and ratio were within the population reference interval despite the presence of monoclonal intact immunoglobulin in serum. In other patients with monoclonal gammopathy of undetermined significance, values were abnormal although there was no clinical evidence of progression to multiple myeloma. Conclusions: The use of free-light-chain measurements alone cannot differentiate some groups of patients with monoclonal gammopathy from healthy individuals. As with the introduction of any new test, it is essential that more scientific data about use of this assay in different subject groups are available so that results can be interpreted with clinical certainty. (C) 2003 American Association for Clinical Chemistry.